Extractive distillation of alcohols with glycol ethers



July 3, 1951 P. V. SMITH, JR., ETA EXTRACTIVE DISTILLATION OF ALCOHOLSWITH GLYCOL ETHERS Filed lay l, 1948 FmcnoNATozs- Paul V-'5m1.th,Jr.Carl 6. Carlson.

SMGd-Lornag Patented July 3, 1951 EXTRACTIV E DISTILLATION OF ALCOHOLSWITH GLYCOL ETHERS Paul V. Smith, Jr., Westfield, and Carl S. Carlson,

Elizabeth, N. J., assignors to Standard Oil Development Company, acorporation of Delaware Application May 1, 1948, Serial No. 24,496

14 Claims- (Cl. 202-395) This invention relates to a practical method ofseparating close-boiling oxygenated organic compounds and is concernedwith the controlled use of a relatively high-boiling glycol-ether as arefluxing medium in a continuous fractional distillation of theclose-boiling oxygenated compounds.

In copending application, Serial No. 768,440, filed August 13, 1947, itis proposed to fractionate close-boiling oxygenated compounds byfractionally distilling the oxygenated compounds in the presence of alarge excess of a hydrocarbon oil which is liquid under the conditionsobtaining in the fractionation zone. In such a system the volatilitiesof the compounds are altered to such an extent that separations arepossible which are diflicult to obtain by ordinary fractionation.

There are, however, a number of disadvantages in employing straighthydrocarbons as a reflux medium in separating such oxygenated compounds.In the first place, solubility relationships are such that only smallamounts of water can be present without'separation of two liquid phases.Such liquid phase separation is generally quite undesirable in suchsystems since it results in loss of selectivity. Furthermore, in orderto prevent entrainment of the hydrocarbon overhead with the alcoholproducts, both in the fractionation stage and in the subsequent stage ofstripping the alcohol from the hydrocarbon, it is necessary to use ahydrocarbon of relatively high initial boiling point. This high initialboiling point of the hydrocarbon results in high tower temperatures andin the necessity for using large amounts of high pressure steam forreboiling.

It is, therefore, an object of this invention to provide a commerciallyfeasible process for the efllcient separation of close-boilingoxygenated compounds which are difficult to separate by ordinaryfractional distillation methods, while avoiding the difficulties oflimited miscibility and high boiling point encountered when usinghydrocarbons as the refluxing medium.

The objects of this invention are accomplished by fractionating themixture of close-boiling oxygenated compounds in the presence of a largeexcess of a glycol-ether.

The process of this invention is best applied to distillation cuts ormixtures, the components of which distill within a narrow range;however, it may be applied to wide-boiling mixtures as well. Theinvention is particularly directed to the separation of alcohols ofdifferent types and molecular weights from one another and to theseparation of alcohols as a class or one particular alcohol from otheroxygenated compounds such as ketones, acetals, esters, aldehydes, etc.,and is useful preferably in separating between compounds boiling in therange of normal propyl alcohol, secondary butyl alcohol and higherboiling compounds. Lower boiling mixtures cannot be separated withoutencountering reversal of volatility. For example, a mixture of ethanoland isopropanol cannot be separated by the present invention withoutrendering isopropanol more volatile than ethanol. Typical separationswhich can be made are n-propyl alcohol from sec-butyl alcohol, n-propylalcohol from i-butyl alcohol, n-propyl alcohol from a mixture ofsec-butyl and i-butyl alcohols, n-propyl alcohol from ethyl butylketone, n-propyl alcohol from valeraldehyde, n-propyl alcohol from amixture of C4 and higher molecular weight alcohols, n-propyl alcoholfrom a mixture of C5 and higher molecular weight carbonyl compounds, andn-butyl alcohol from isomeric C5 and higher alcohols.

The crude oxygenated mixture may contain amounts of water greater than,less than, or equal to the amounts corresponding to azeotropiccompositions, but in any case it must be miscible with the solvent inall portions of the fractionation zone.

Some of the above-described mixtures are obtained by an olefin hydrationreaction, e. g., when a mixture of ethylene and propylene is absorbed insulfuric acid, diluted, hydrolyzed, and a resulting aqueous alcoholmixture is stripped out. Another important source of such mixtures isthe Fischer synthesis hydrogenation of carbon monoxide, especially whenthe aqueous layer product formed contains not only lower primary andsecondary alcohols but also various ketones, aldehydes, ethers, acetals,esters, carboxylic acids and certain tertiary alcohols. Still anothersource is in the products of hydrocarbon oxidation where both oil andwater layers are obtained, each containing oxygenated organic compounds.Narrowboiling range mixtures which may be obtained by the ordinarydistillation processes from aqueous solution are as follows:

The narrow-boiling range mixture may be a binary or tertiary mixture asin the groups shown, but generally the crude mixtures contain additionaloxygenated organic compounds, which do not interfere with the basicoperation of this invention in isolating the principal alcoholcomponents of the mixtures.

A typical crude propanol cut obtained from the water layer of a Fischersynthesis process contains the following:

TABLE II Normal propanol cut 7 Normal Binary Water Component BoilingAzeotrope Pt. B Pt., (3

Ethanol 78. 5 78. l Isopropano 82. 4 80. 4 n-Propanol 97.8 87.7 Sec-Bum99. 5 87. 5 iso-Butanol 107.3 89. 9 n-Butaucl 117.7 92.2 tert-Butanol82. 8 79. 9 lee-Prop l Acetate 89. 4 l 75. 5 n-Prop Aoeta 101. 6 82. 4Methy Ethyl Ketone 79.6 74.8 Methyl n-Propyl Ketone.. 102. 3 82. 9Methyl iso-Propyl Ketone. 94. 3 Diethyl Ketone 102. Methyl iso-ButylKetone. 116. 8 Ethyl Propionate 99. 1 81. iso-Valeraldehyde 92. 82n-Valeraldchyde. 103. 7 80. 6 Methyl n-Butyl Ketone 127. 2

'lernary with ethyl alcohol.

In the above cut, the kinds and relative quantities of the componentsvary greatly but the major components are propanol, secondary butanoland methyl normal butyl ketone. when this cut is distilled from aqueoussolution, many of the compounds form azeotropes with water and withthemselves with the result that the boiling points are brought so closetogether that separation is very diflicult to achieve. The difilcultiesencountered can be appreciated by reference to Table II which shows theoverlapping of the anhydrous and binary aqueous azeotrope boilingpoints.

To obtain the desired separation of purified organic components frommixtures like that mentioned with benefits of the present invention, themixture is subjected to a continuous fractional distillation in a columnof practical size, including a primary rectification zone, a secondaryrectification zone, above the primary zone, and a stripping zone belowthe primary zone for countercurrent vapor liquid contact under reboilingand refluxing conditions. A sufiiciently large quantity of aglycol-ether is introduced at the upper part of the primaryrectification zone to effectively modify the relative volatilities ofthe organic compounds to be separated and to distill a larger part ofone component or group of components than of another component oranother group of components from the internal reflux.

The separation can be effected in a continuous manner under steady stateconditions to obtain product streams of desired purities and constantcompositions while supplying the large quantity of glycol-ether to theupper part of the rectification zone. The temperature of theglycol-ether introduced into the primary rectification zone ispreferably close to the temperature of the liquid on its feed plate,although it may be lowered to partially condense vapors ascending to thesolvent feed plate.

Since the efficient operation is essentially con- 4 tinuous, theglycol-ether is added continuously near the top of the primaryrectification zone of the column while the mixture of oxygenated organiccompounds to be separated is fed continuously into the column at a lowerpoint while sufficient heat is provided to afford distillationthroughout the column.

The feed stream of the oxygenated organic compounds is preferablyintroduced into the fractionating column between the primaryrectification zone and the lower stripping zone at a point where theratio of the main organic compounds to be separated in the feed issimilar to the ratio of these compounds in the internal refluxdescending through the column.

The feed stream is preferably preheated to a temperature close to thatof the internal liquid reflux under practically equilibrium boilingconditions at the point of introduction. The preheated feed stream maybe liquid, partially vaporized, or completely vaporized when introducedinto the fractionating column.

Vapors of the organic compounds introduced as a feed stream at thebottom part of the primary rectification zone in the fractionatingcolumn pass up through the primary rectification zone in contact withdescending internal liquid reflux under practically equilibriumreboiling and refluxing conditions. The secondary rectification zoneserves to strip glycol-ether from the overhead vapors.

The quantity of glycol-ether required to be introduced continuously atthe upper part of the primary rectification zone for accomplishing thedesired separation of the close-boiling compounds is considerablygreater than the quantity of condensate with which it becomeshomogeneously mixed. This is necessary in order to make the glycol-etherconcentration of the internal reflux substantially above a criticalminimum in the range of -99 volume percent. With adequate glycol-etherconcentration in the internal reflux for efiecting the separation, theorganic component to be isolated in the bottoms is dissolved in theinternal reflux that reaches the bottom part of the primaryrectification zone and finally the bottom of the stripping zone.

The minimum concentration in the internal reflux of the glycol-ether forobtaining the separation depends on the particular organic compounds tobe separated and varies between 'm t iiid 99 volume percent. In alimiting case of isolating n-propyl alcohol from sec-butyl alcohol,essentially no separation is effected if the internal reflux containsless than volume per cent glycol-ether, and for obtaining satisfactoryresults on a practical scale. more than volume percent glycol-ether,preferably 90-99 volume percent, is required in the internal liquidreflux. As the dilution of the internal reflux becomes infinite, theselectivity of separation is increased but the operating efiiciency isexcessively lowered on account of the relatively small quantities of theoxygenated organic compounds being processed.

Under steady state conditions existing in a continuously operatingfractional distillation zone, the internal reflux having adequateconcentration for accomplishing the separation of the close-boilingalcohols and other oxygenated compounds, there tends to be a nearlyconstant glycol-ether concentration in the homogeneous liquid phase oneach plate above the feed point and on each plate below the feed pointalthough the average concentration on the plates above and below thefeed point may differ. This internal reflux in flowing from the top tothe bottom becomes richer in the oxygen compounds having the lowestrelative volatility in the presence of the glycol-ether while the oxygencompounds having the highest relative volatility in the glycol-ether aredistilled overhead.

The overhead vapors from the secondary rectification zone are enrichedin one or more of the organic components rendered relatively morevolatile by concentration of the glycol-ether in the liquid reflux whilethe remaining portion of the organic material introduced with the feedremains dissolved in the internal reflux. For example, in distilling anaqueous mixture of two alcohols,.the distillation may be carried out sothat either one of the alcohols is obtained free of the other. Inseparating n-propanol from secondary butanol the distillation may be conducted so that n-propanol is obtained overhead and a mixture ofn-propanol and sec-butanol is obtained in the bottoms or a portion ofthe secondary butanol may be taken overhead with the n-propanol so thatsecondary butanol free of npropanol is obtained in the bottoms.

The functioning of the stripping zone may be described as follows:

The mixture of the close-boiling alcohols and other oxygenated compoundsto be separated, as in the liquid reflux from the bottom of therectiflcation zone, flows downwardly through the stripping zone incountercurrent contact with ascending vapors evolved from the solutionunder reboiling conditions. A sufliciently high concentration ofglycol-ether is maintained in the liquid flowing dOWn through thestripping zone, as in the rectification zone, to make the liquidprogressively richer in oxygenated compounds having the lowest relativevolatility in the glycolether while the oxygenated compounds having thehighest relative volatility in the glycol-ether are stripped from theliquid. Under practically equilibrium reboiling 7 and refluxingconditions for complete stripping in the stripping zone, the organiccompounds rendered more volatile may be removed as vapor overhead fromthe stripping zone at the same rate that they enter the invention, thesebeing indicative, however, of but a few of the various ways in which theprinciples of the invention may be employed.

This invention will be described in detail as applied to the separationof n-propyl alcohol and sec-butyl alcohol from aqueous solution.

Referring to the drawing, a feed fraction is introduced by line 3 intotower I where it is fractionated in the presence of a liquid stream of aglycol-ether introduced through line 4, at a point several plates belowthe top of the tower. The conditions in the tower are such as to cause adistillation of the alcohol compounds in the presence of theglycol-ether on each plate of the tower. A suflicient amount of theglycol-ether is added so that it is present to the extent of 90 volumepercent on each plate. As the vapors of the feed pass up the column someof them are dissolved in the large excess of glycol-ether descending thecolumn and are collected together with the glycol-ether in pools on eachplate. Conditions are maintained on each plate of the tower such thatthe liquid mixtures of the n-propyl and sec-butyl alcohols are at theirboiling points and are continuously being contacted with vapors boiledfrom the plates below. Because of the enhanced volatility of then-propyl alcohol in relation to the sec-butyl alcohol the vapors arerelatively rich in the former and poor in the latter. -By maintainingthe amount of glycol-ether on each plate so large that infinite dilutionis approached, the optimum relative volstripping zone as part of theliquid feed to this zone and a solution of the organic compoundsrendered less volatile freed of the more volatile compounds in theliquid may be withdrawn from a bottom part of the stripping zone.

Suitable glycol-ethers to be used in the process of the presentinvention include monomethyl ether of ethylene glycol, the mono-ethylether of ethylene glycol, the n-propyl ether of ethylene glycol, theisopropyl ether of ethylene glycol, the monobutyl ether of ethyleneglycol, the monomethyl ether of diethylene glycol, the monoethyl etherof diethylene glycol, the mono-normal propyl other of diethylene glycol,the monoisopropyl ether of diethylene glycol, the monobutyl ether ofdiethylene glycol, the diethyl ether of ethylene glycol, the diethylether of diethylene glycol, the dibutyl ether of ethylene glycol, thedibutyl ether of diethylene glycol, dimethoxy tetraglycol,dibutoxytetraglycol, and the corresponding derivatives of propyleneglycol or polypropylene glycols.

In the accomplishment of the foregoing and related ends, the inventionthen comprises the features hereinafter fully described, andparticularly pointed out in the claims, the following description andthe annexed drawing setting forth in detail certain illustrativeembodiments of the atilities for the separation of the desiredcomponents can be secured. Furthermore, by controlling the amount ofoxygenated compound reflux and consequently the reflux ratio and thenumber of plates, the actual degree of separation may be varied untilthe desired product purity and recovery are obtained. Thus, suitabletemperature and reflux conditions are maintained in the tower so thatsubstantially pure n-propyl alcohol appears in the overhead stream and asolution of sec-butyl alcohol in glycol-ether appears in the bottomsproduct. The plates above the point of glycol-ether entry serve to stripglycolether from the alcohol overhead. Any water present in the feedwill appear with the overhead alcohol product.

Overhead vapors consisting substantially of pure n-propanol and all thewater entering with the feed are withdrawn from the top of column Ithrough line 5 by which they are passed through condenser 6 to areceiver I. A portion of the condensate collected in receiver I isreturned to the top part of the column I as external reflux through line8. The remaining portion of distillate collected in receiver I iswithdrawn through line 9 as a product.

Bottoms liquid consisting of a solution of secbutyl alcohol inglycol-ether collected at the lower part of column I is passed by lineIII into reboiler I I for heating by indirect or direct heat exchangewith a heating medium such as livetables showing the application of thisinvention to the separation of ethanol and isopropanol and of normalpropanol and secondary butanol. The

TABLE III Relative volatility of EtOH to IpOH Charge: 20

Moi percent EtOH) }Blnary Moi percent lpOIIl Basis... 'ol. percent ButylCcllosolve.

\apor Sample:

M01 percent EtOH 78.9 80.6 Mol percent lpOH 21.1 19.4 Liquid Sample:

Mol percent EtOH.. 80. M01 percent lpOl-l.... 19 Relative Volatility ofEtOH to XPOH l 0.91

Normal volatility in absence of solvent EtOH over IpOH, l.l5. Nora:EtOll=etliyl alcohol; IpH=isopropyl alcohol; Butyl 3QCellosolve=monohutyl ether of ethylene glycol.

RunNo. l i 2 aw noon 0 8 cific examples of the same given, what isclaimed as new and useful and desired to be secured by Letters Patentis:

1. The method of separating lower and higher molecular weight saturatedmonohydric alcohols containing 3 to 5 carbon atoms per molecule andhaving normal boiling points above that of isopropanol and which formclose-boiling mixtures difficult to separate by ordinary fractionaldistillation, which comprises continuously introducing a feed mixture ofsaid alcohols to a fractional distillation zone wherein vapors of saidalcohols ascend counter-currently to liquid reflux of the alcoholsdissolved in "IO-99 volume per cent of a glycol ether to effectvaporization of lower molecular weight alcohol continuously removingvapor of lower molecular weight alcohol overhead from the fractionaldistillation zone, and removing a solution of higher molecular weightalcohol in the glycol ether as bottoms. p

2. A process according to claim 1 in which the alcohols are aqueousalcohols. I

3. A process according to claim 1 in which the alcohol mixture comprisesn-propanol and sec-butanol and in which a mixture of n-propanol andsec-butanol is removed overhead and a solution of sec-butanol alcohol inthe glycol ether is removed as bottoms.

4. A process according to claim 1 in which TABLE IV Relatwe volatzlztyof ethanol to lsopropanol Run No 6 7 8 9 10 Charge:

Mol Per Cent EtOH 80 80 80 20 M01 PM Cent lpOH... Binary Basis 20 20 8020 80 Vol. ler (cm Ethyl Carbitol l 90 80 80 70 70 Vapor Sample;

M01 Per Cent EtOl'l 78. & 77.6 16. 7 78.3 18 4 M01 For Pent lpOli 21. 222.4 83.3 21. 7 81 6 Liquid Sample:

Mol Per (ent EtOl-l 79. 6 81.0 22. l 80. 7 20 7 Mol Per Cent lpOH 20.419.0 77.9 19.3 79 3 Relative Volatility of EtOl-l to 1pOH.. 0. 953 0.8120 707 0.863 0 865 Normal volatility in absence of solvent: EtOH overIpOH, 1.15. 1 N OTEZ Ethyl carbitol=monoetl1yl other of diethyleneglycol.

TABLE V Relative volatility of normal propanol to secondary butanol RunNo ll 12 13 14 it? c on M01PerCentsccBl1OH} 30 20 30 Vol. Per CentRionobutyl ether of ethylene glycol 90 90 Vol. Per Cent Monoethyl etherof diethylcne glyc0l.... 9O 90 Vapor Sample:

M01 Per Cent n-PrOH 78.9 87.4 77.6 85.8 M01 Per Cent sec'BuOH 2L1 12.622. 4 14. 2 Liquid Sample:

Mol Per Cent n-PrOH 62. 8 73. 8 63. 7 75. 2 Mol Per Cent scc-BuOH 37. 226 2 36. 3 24. 8 Relative Volatility of n-PrOH over sec- BuOH 2.21 2. 461.97 1.99

- tion having been thus fully set forth and spe- 75 the alcohol mixturecomprises n-propanol and sec-butanol and in which normal propyl alcoholis removed overhead and a solution of normal propyl alcohol andsecondary butyl alcohol in the glycol ether is removed as bottoms.

5. In a. process of separating aqueous azeotropic mixtures of lower andhigher molecular weight saturated monohydric alcohols containing 3 to 5carbon atoms per molecule and having normal boiling .points above thatof isopropanol and which form close-boiling mixtures dimcult to separateby ordinary fractional distillation, the steps which comprisecontinuously passing vapors of said alcohols up through a primaryrectification zone wherein the alcohol vapors ascend in contact with ac'ountercurrent internal reflux comprising condensate from said vaporscontaining -99 volume per cent of a glycol ether, continuouslyintroducing said glycol ether into the condensate at an upper part ofthe primary rectification zone, continuously passing from said primaryrectification zone into a secondary rectification zone the vapor of oneof said alcohols volatilized to a greater extent than another of saidalcohols having a higher molecular weight by the increased glycol ethercontent of the internal reflux wherein said vapors are further rectifiedto condense accompanying boiling points above that of isopropanol andwhich are diflicult to separate by ordinary fractional distillation,which comprises continuously introducing a feed mixture of the alcoholsto a rectification zone wherein vapors of the feed mixture ascendcountercurrently in contact with a liquid reflux comprising condensatefrom said vapors containing 70-99 volume per cent of a glycol ether,increasing the glycol ether content of the condensate at an upper partof the rectification zone by introducing glycol ether continuouslythereto in excess of the amount of glycol ether leaving said zone asvapor, introducing internal liquid reflux from a bottom part of therectification zone to a stripping zone, passing said reflux incountercurrent contact with vapors boiled from the internal liquidreflux as it flows down to a bottom part of the stripping zone,withdrawing from the top part of the rectification zone water and lowermolecular weight alcohol, withdrawing from the bottom part of thestripping zone an 'anhydrous solution of higher molecular weight alcoholdissolved in the glycol ether.

7. A process as in claim 6 in which the glycol ether is the monobutylether of ethylene glycol and in which its content in the internal refluxis 8099 volume per cent.

8. In a process of separating aqueous azeotropic mixtures of n-propylalcohol and secbutyl alcohol, the steps which comprise continuouslypassing a solution of n-propyl alcohol in a glycol ether containingsec-butyl alcohol down through a stripping zone so that a liquid portionof the solution flows countercurrently in contact with vapors evolvedtherefrom under constant refluxing and reboiling conditions, maintaininga glycol ether content of 80-99 volume per cent in the resultinginternal reflux to effect vaporization of a larger part of the n-propylalcohol than of the sec-butyl alcohol in said reflux, continuouslywithdrawing vapors of alcohols and water overhead from the strippingzone, the n-propyl alcohol being thus withdrawn as vapor at essentiallythe same rate that the n-propyl alcohol dissolved in said glycol etherenters the stripping zone, and withdrawing from a bottom part of thestripping zone a solution of sec-butyl alcohol in the glycol ethersubstantially free of n-propyl alcohol and water.

9. A process ccording to claim 8 in which the glycol ether is themonobutyl ether of ethylene glycol, and in which its content in theinternal liquid reflux is 9099 volume per cent.

10. A process according to claim 8 in which the glycol is the monoethylether of diethylene glycol.

11. In a process of separating normal propyl alcohol from its aqueousmixtures with saturated monohydric higher-boiling alcohols containing upto 5 carbon atoms per molecule the steps which comprise continuouslypassing a solution of a mixture of normal propyl alcohol and higheralcohols in a glycol ether down through a stripping zone so that aliquid portion of the solution flows countercurrently in contact withvapors evolved therefrom under constant refluxing and reboilingconditions, maintaining a glycol ether content of -99 volume per cent inthe resulting internal reflux to effect vaporization of a larger part ofthe normal propyl alcohol than of the higher-boiling alcohols in saidreflux, continuously withdrawing vapors of normal propyl alcohol andwater overhead from the stripping zone, the normal propyl alcohol beingthus withdrawn as vapor at essentially the same rate that the normalpropyl alcohol dissolved in said glycol ether enters the stripping zoneand withdrawing from a bottom part of the stripping zone a solution ofsaid higher-boiling alcohols in the glycol ether substantially free ofnormal propyl alcohol and water.

12. A process according to claim 11 in which the glycol ether is themonobutyl ether of ethylene glycol and in which its content in theinternal liquid reflux is -99 volume per cent.

13. A process according to claim 11 in which the glycol ether is themonoethyl ether of diethylene glycol.

14. A process according to claim 11 in which the higher-boiling alcoholsare alcohols having 4 carbon atoms per molecule. I

PAUL V. SMITH, JR. CARL S. CARLSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,273,923 Bludworth Feb. 24, 19422,339,576 Luten Jan. 18, 1944 FOREIGN PATENTS Number Country Date563,164 Great Britain Aug. 1, 1944

1. THE METHOD OF SEPARATING LOWER AND HIGHER MOLECULAR WEIGHT SATURATEDMONOHYDRIC ALCOHOLS CONTAINING 3 TO 5 CARBON ATOMS PER MOLECULE ANDHAVING NORMAL BOILING POINTS ABOVE THAT OF ISOPROPANOL AND WHICH FORMCLOSE-BOILING MIXTURES DIFFICULT TO SEPARATEE BY ORDINARY FRACTIONALDISTILLATION, WHICH COMPRISES CONTINUOUSLY INTRODUCING A FEED MIXTURE OFSAID ALCOHOLS TO A FRACTIONAL DISTILLATION ZONE WHEREIN VAPORS OF SAIDALCOHOLS ASCEND COUNTER-CURRENTLY TO LIQUID REFLUX OF THE ALCOHOLSDISSOLVED IN 70-99 VOLUME PER CENT OF A GLYCOL ETHER TO EFFECTVAPORIZATION OF LOWER MOLECULAR WEIGHT ALCOHOL CONTINUOUSLY REMOVINGVAPOR OF LOWER MOLECULAR WEIGHT ALCOHOL OVERHEAD FROM THE FRACTIONALDISTILLATION ZONE, AND REMOVING A SOLUTION OF HIGHER MOLECULAR WEIGHTALCOHOL IN THE GLYCOL ETHER AS BOTTOMS.